From increased drowsiness to disrupted REM cycles, here's what happens when you booze before you snooze

For most people, a glass of wine before bed sounds like a luxurious nighttime ritual—it's delicious and it gets you in the mindset for relaxation. Anyone who's had a few drinks before hitting the hay can tell you about alcohol's power to put you to bed, but its effects don't end once you shut your eyes. Is that nightcap a good or bad idea?

Here, Wine Spectator rounds up the latest scientific research to break down what wine lovers need to know about alcohol and sleep.

Wine Can Help You Fall Asleep …

Tossing and turning? Whether it's stress from work, the latest binge-worthy show or a chronic condition that's keeping you up at night, you're not alone. About 70 million Americans have some sort of trouble sleeping, according to the American Academy of Sleep Medicine. For many, alcohol is an accessible, and often appealing, option for relief.

Studies have shown that drinking before bed reduces sleep latency, meaning it can help bring on sleep more quickly than usual. This is thanks to alcohol's sedative effects, which range in intensity depending on one's blood-alcohol content (BAC). However, several studies have also shown that people can develop a tolerance to these sedative effects in as few as three nights. Eventually your body will need more alcohol to experience sleep-inducing effects, which can lead to even bigger problems, such as alcohol dependency.

Of the eight grape varieties tested, Nebbiolo contained the most melatonin, with 0.965 nanograms per gram of grape skin (ng/g), followed by local Italian grape Croatina (0.87 ng/g) and Barbera (0.63 ng/g). Cabernet Franc, on the other hand, contained only trace amounts of melatonin, at 0.005 ng/g. But research has not determined whether wine's melatonin content could make it a smarter choice than others for pre-bed drinking.

… It Might Not Be Quality Rest

Even though a tipple may help you drift off to dreamland, you might not enjoy a satisfying slumber throughout the night. Studies have shown that, particularly when consumed at levels exceeding moderation, alcohol suppresses rapid eye-movement (REM) sleep—the phase of sleep that's associated with dreaming and retaining memories—during the first part of the night.

It gets worse as the night goes on. A 2015 study published in Alcoholism: Clinical and Experimental Research showed that while subjects who drank experienced an increase in slow-wave sleep, or "deep sleep," early in the night, a few hours later, they experienced sleep disruption, greater numbers of awakenings and more time spent awake.

By monitoring electrical impulses in the brain, the study's researchers found that those who drank alcohol experienced during the second half of the night what's known as alpha-delta sleep—meaning that alpha waves (associated with calm wakefulness) and delta waves (associated with the deepest level of sleep) were occurring at the same time. Dr. Christian Nicholas, a University of Melbourne researcher involved in the study, explained that these findings indicate that alcohol impairs the normal restorative effects of sleep.

These unwanted occurrences during the second half of sleep tend to happen around the same time that alcohol is metabolized, a phenomenon known as the "rebound effect." As described by sleep-medicine specialists Dr. Timothy Roehrs and Dr. Thomas Roth in an article published by the National Institute on Alcohol Abuse and Alcoholism, during the first half of sleep, the body adjusts certain sleep variables (such as the amount of REM sleep or slow-wave sleep) to the presence of alcohol in order to maintain a normal sleep pattern.

Once the alcohol is cleared from the system—which would take about four to five hours for someone who went to sleep with a BAC of 0.08—some of these adjustments change in the opposite direction, causing wakefulness and lighter stages of sleep. This also explains why, after a particularly long night of drinking, you may wake up early and feel wide-awake.

How Alcohol Affects Sleep Disorders

According to Dr. Ilene Rosen, program director of the University of Pennsylvania Sleep Fellowship and president of the American Academy of Sleep Medicine, alcohol likely affects people with sleep disorders differently than those with healthy sleep patterns. For example, she told Wine Spectator that insomniacs tend to enjoy increased sedative effects of small doses of alcohol without sleep disruption later on.

However, like healthy sleepers, insomniacs can still develop a tolerance to these effects, so Rosen says alcohol is never recommended as a sleep aid. Further, those who take sleep medication should exercise extreme caution in regard to alcohol, as the side effects of mixing the two can be dangerous, or even deadly.

Rosen, who specializes in sleep apnea, also noted that alcohol could exacerbate breathing problems during sleep. "Individuals who have sleep apnea should avoid alcohol in the evening," she said via email. "In addition, if you or your bed partner notice an increase in loud snoring or breathing pauses while sleeping after consuming alcohol, please discuss this with your physician."

What's a Wine Lover to Do?

Ultimately, disrupted sleep can be responsible for daytime sleepiness and poor performance throughout the next day. One of the first rules a wine lover can follow in order to sleep soundly and avoid a foggy mind the following day is to wait a while between drinking and sleeping, since many of the problems associated with alcohol and sleep are due to the rebound effect, and can be avoided if you sober up while you're awake.

"If someone wants to have one 5-ounce glass of wine or one 12-ounce beer with dinner, allowing for three hours after consumption before going to bed may be sufficient," Rosen said, though the exact time also depends on body weight and the time it takes for an individual to metabolize alcohol.

But even if you don't have hours to spare, there are some basic steps you can take to be able to enjoy an adult beverage at night and still sleep like a baby afterward. "There are certain habits that people need to maintain in order to optimize their sleep quality," explained Dr. Camilo Ruiz, medical director of Choice Physicians Sleep Center in Fort Lauderdale, Fla. "They need to have routine bedtimes that are maintained throughout the week—not just during the workweek but also on the weekends. Some people cut back on their sleep during the workweek because they want to get work done, and then on the weekends they'll sleep in. Unfortunately, that doesn't allow for restful sleep."

Ruiz also suggests avoiding bright lights in the evening, as it disturbs the circadian rhythm, the internal clock that regulates sleepiness and alertness. So even if you do have a bit of alcohol in your system, if you shut the blinds, turn off the television and keep you phone out of sight, you will be less likely to throw your sleep schedule totally out of whack.

While you're at it, Ruiz suggests setting your whole sleeping space up for success. "You want a dark and cool environment," he explained, adding that environmental disturbances such as nocturnal pets or a snoring bed partner will make it tough to get a sound sleep, especially if alcohol is involved.

Finally, as with most wine-and-health issues, moderation is key. "One or two glasses of wine … at night might relax the body enough so that it can achieve good sleep," Ruiz said. "The problem is when people go out and binge drink; there's the potential for serious problems … I think with everything in life, moderation is good."

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